This invention relates in general to a boat support structure and, in particular, to an improved boat support structure permitting interchangeable gimbaling or non-gimbaling support of a roller on a shaft suitable for incorporation in a boat trailer or boat transporting vehicle structure.
A roller mounted rotatably on a shaft is frequently used to support an article that is moved over the roller in a direction crosswise to the shaft. Typically, the roller includes a generally cylindrical outer periphery and a hub structure connected to support the roller on the shaft. In many instances, the outer cylindrical periphery of the roller is coaxial of the center axis of the mounting shaft during roller rotation, and the roller moves in a plane normal to the shaft axis during such rotation without a wobbling effect.
In certain roller installations in support of boat structures, it is desirable to permit the roller to cant or tilt relative to the shaft during rotation, thereby angling the outer periphery of the roller relative to the center axis of the shaft. Through such cant support, the roller moves in planes angled other than normal to the shaft axis resulting in a wobbling effect. This latter action of the roller will be referred herein as gimbaling rotation while the maintenance of roller rotation in planes normal to the axis of the shaft will be referred to as non-gimbaling rotation.
Gimbaling rotation of a roller is advantageous where a boat hull of varying shape is moved over the support rollers of the trailer and the like while loading or unloading the boat into or from the water. Even when a relatively large number of rollers are used to support the boat, it is desirable to have each roller self-align to cause its tread to engage the hull across its full tread width, as compared to much smaller engagement along only an outer edge of the tread. A gimbaling roller thereby automatically self-aligns and allows the full tread to follow and engage the changing contours of the hull and thereby minimize stress concentrations of the hull.
On the other hand, it is frequently desirable, even in the same example of a boat trailer, to maintain certain rollers in a stable non-gimbaling position such as, for example, to increase the load carrying capacity of the rollers. Consequently, it can be advantageous in many installations to provide both non-gimbaling and gimbaling rollers, and allow the user to interchange such respective mountings as desired. Prior art roller supports require the user to resort to elaborate physical modifications requiring extra parts and tools to interchange such selective alternative mounting of respective rollers as needed.